Field of the Invention
The application relates in general to an illumination technology, and in particular, to a lens structure which can be applied to direct-type backlight technology or illumination lamps with a better light extraction uniformity, and to a lamp, a backlight module, and a display device using the lens structure.
Description of the Related Art
Current illumination technology (e.g. direct-type backlight modules or lamps) usually uses secondary optical lenses to achieve the desired optical effect based on the consideration of thickness, cost and so on. Nowadays, these secondary optical lenses are divided into two categories: the reflective type and the refractive type. Specifically, the light mixing distance of the reflective lens is greater than that of the refractive lens, and thus the reflective lens can use fewer light-emitting diodes (LED) to achieve the desired optical effect.
FIG. 1A is a schematic view illustrating the light extraction method of a conventional reflective lens. As shown in FIG. 1A, the conventional reflective lens 300 includes a total internally reflect (TIR) surface 302 which can reflect light L emitted from a light-emitting diode 304 to exit from a light output surface 306 at the side of the conventional reflective lens 300. However, this light extraction method may easily cause the user to see a shadow cast by the top of the conventional reflective lens 300 (i.e. above the TIR surface 302).
Therefore, a lens structure that can prevent the shadow problem and has a better light extraction uniformity is needed.